Method of manufacture of color television picture tube



June 8, 1965 J. P. FIORE 3,137,404

METHOD OF MANUFACTURE OF COLOR TELEVISION PICTURE TUBE Original Filed Jan. 11, 1962 4 Sheets-Sheet 1 J. P. FIORE June 8, 1965 METHOD OF MANUFACTURE OF COLOR TELEVISION PICTURE TUBE 4 Sheets-Sheet 2 Original Filed Jan. 11, 1962 (PRIOR ART INVENTOR. Jose h PFiot'e BY W June 1965 J. P. FIORE 3,187,404

METHOD OF MANUFACTURE OF COLOR TELEVISION PICTURE TUBE Original Filed Jan. 11, 1962 4 Sheets-Sheet 5 I Ema 6| Joseph]? Fz'ore J. P. FIORE June 8, 1965 METHOD OF MANUFACTURE OF COLOR TELEVISION PICTURE TUBE 4 Sheets-Sheet 4 Original Filed Jan. 11, 1962 INVENTOR. Joseph J? Fiore 6 I o ziiy.

6 Claims. 01. 29-2515 This invention relates to new and improved methods of manufacturingcolor television picture tubes.

This application is a division of the copending application of Joseph P. Fiore, Serial No. 165,476, filed I anuary 11, 1962, for Color Television Picture Tube and Method of Manufacture, and assigned to the same assignee as the present application.

The color television picture tubes now in commercial use are of the type comprising a mosaic tri-col-or phosphor screen and a color-selection device in the form of a shadow mask having an aperture pattern corresponding to the distribution pattern of the component phosphors in the mosaic screen, in conjunction with three electron guns for projecting separate electron beams through the mask onto the phosphor screen at difierent angles. Col-or selection is achieved by selectively controlling the intensities of the electron beams. In order to achieve faithful color reproduction, it is essential that the spacing and alignment of the color-selection aperture mask with re-' spect to the mosaic phosphor screen be precisely determined; even very slight rotational or longitudinal misalignment or mis-orienta-tion of the mask with the screen leads to color contamination and consequent degradation of both color and monochromatic images.

' In the manufacture of such tubes, it has been conventional practice to fabricate the envelope in sections which are sealed together after completion of the mask-andscreen assembly. conventionally, the envelope comprises a faceplate section which is composed of an end or screen portion of substantially spherical curvature and an integral rim portion or skirt extending outwardly from the screen portion toward the electron gun assembly. The remainder of the tube envelope comprises a funnel section adapted to be sealed to the rim portion of the faceplate section, and a neck section which is sealed to the funnel and which houses the electron gun assembly. The mosaic phosphor screen is formed on the internal surface of the screen portion of the faceplate section, the mask is then mounted to the rim portion of the faceplate section, and the faceplate and funnel sections are frit-sealed together to complete the tube assembly.

In order to secure the requisite degree of precision in the alignment of the mask and screen assembly, the customary practice is to form the screen by photographic processes including exposure of a photo-sensitive resist through the mask to fix the areas on the internal surface of the screen portion of the faceplate to which a phosphor applied by a slurry process will adhere. The photographic exposure process is repeated severaltimes, once for each component phosphor of the mosaic screen, and this of course involves removal and reinsertion of the mask as an incident to the screen forming process. It is therefore essential that the mounting arrangementfor the mask be sumciently rigid and precise to define a unique mask position, both during the screen processing and in the subsequent final assembly of the tube.

The mask mounting arrangement now employed in conventional color television picture tubes involves the provision of mounting studs or pins which are fused into the rim portion of the faceplate and whichmate with generally triangular apertures in cantilever-mounted leaf 3,1814% Patented June 8, 1965 point, at which time the pins are inserted and the faceplate cooled. After application of the pins in this fashion, it is necessary to re-anneal the entire face-plate section to relieve strains produced by the localized softening of the glass, and the re-annealing process involves re-heating the entire faceplate above the strain point of the glass and slowly cooling to an ambient temperature well below the strain point. This leads to sagging of the faceplate and, sometimes, to slight mis-alignment of the pins, with the result that the studded faceplate section is often found to fall outside the narrow and highly critical dimensional tolerance range for faceplate curvature and/or pin alignment. In mass production, an excessively high proportion of studded faceplate sections must be scrapped despite the exercise of every available precaution, and this of course substantially increases the per unit manufacturing cost of completed tubes.

Accordingly, it is a principal object of the invention to provide a new and improved method of manufacturing color television picture tubes, in which the screen curvature and other critical dimensions of the faceplate section of the envelope may be accurately controlled in production quantities within critically small dimensional tolerance ranges.

It is a further object of the invention to provide a new and improved method for mounting the color-selection device in the faceplate section of a color picture tube envelope.

A more specific object of the invention is to provide a method of manufacturing a mask and screen assembly for a color television picture tube, in which the degree of precision of the spacing and alignment between the mask element and the mosaic phosphor screen is greatly enhanced with respect to that achieved by conventional methods, even in mass production, with an attendant substantial reduction in the cost of manufacturing a color television picture tube.

The invention is directed to the manufacture of a color television picture tube of the :type comprising an envelope having substantial symmetry with respect to a predetermined axis and composed of a glass faceplate section with an end or screen portion and a rim portion,

' and a funnel section sealed to the faceplate section, a

mosaic phosphor screen on the inner surface of the end portion of the faceplate section, and a multi-apertured color-selection device having a rigid frame and a mask element with an aperture pattern corresponding'to the distribution pattern of the component phosphors in the mosaic screen. The invention provides a new and improved mc-thod of mounting the color-selection device in a precise predetermined space relation to the phosphor screen by the use of mating pairs of male and female support members adapted for spring-biased mutual engagement in predetermined respective engagement planes. The mounting method of the present invention comprises the following steps, which are not necessarily performed in the recited sequence. The glass faceplate section is molded and annealed, which may be accomplished by the use of conventional techniques. A first support mem ber of each mating pair is secured to the frame of the color-selection device at circumfereutially spaced locations thereon and in outwardly directed orientation with respect thereto, whereby the first support members are maintained in predetermined mutually spaced relation to each other. The other support member of each mating pair is aflixed to the rim portion of the faceplate section with its plane of engagement with the associated first support member at an accurately predetermined distance from the axis of the envelope, and with the other support members positioned in a circumferential array accurately corresponding to the predetermined mutually spaced relation of the first support members; the other support members may be aflixed to the faceplate section as a part of the molding operation, or by frit-sealing after the faceplate sec-tion has been molded and annealed. The temperature of .the faceplate section is maintained below its strain point at all times except during the molding and annealing operations. After the support members have been affixed to the rim portion of the face plate section, the phosphor screen is formed on the end portion of the faceplate section. To complete the assembly, the mating pairs of support members are brought together to securely mount the colr-selection device to the faceplate section in the desired precise predetermined space relation to the phosphor screen.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is a side view, partly cut away and partly in section, of a color television picture tube manufac tured in accordance with the invention;

FIGURE 2 is a cross-sectional view taken along the line 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary perspective view, partly in section, illustrating the conventional prior art mounting of a color-selection mask and phosphor screen;

FIGURE 4 is an enlarged fragmentary detailed view, partly in section, illustrating the engagement of mating mask mounting members in a conventional prior art color television picture tube;

FIGURE 5 is a view, similar to that of FIGURE 3, of a mask and screen assembly in a color television picture tube manufactured in accordance with the present invention;

FIGURE 6 is a cross-sectional view taken along the line 66 of FIGURE 5;-

FIGURE 7 is a cross-sectional view taken along the line 77 of FIGURE 6;

FIGURE 8 is a plan view, partly cut away and partly schematic, of a manufacturing fixture useful in practicing the method of the present invention;

FIGURE 9 is a fragmentary cross-sectional view taken along the line 9-9 of FIGURE 8;

FIGURE 10 is a cross-sectional view, similar to that of FIGURE 6, illustrating an alternative embodiment of the invention;

FIGURE 11 is a fragmentary perspective view of a portion of the rim portion of a faceplate for use in the method of the present invention;

FIGURE 12 is a plan view, partly schematic, of a manufacturing fixture useful in constructing the embodiment of FIGURES 10 and 11;

FIGURE 13 is a fragmentary cross-sectional view taken along the line 13-4-3 of FIGURE 12;

FIGURES 14a and 14b are fragmentary detailed views, partly in section, taken along the lines 14a--14a and 14b-44b, respectively, of FIGURE 12; and

FIGURE 15 is a fragmentary cross-sectional view, similar to those of FIGURES 6 and 10, illustrating a still further alternative embodiment of the invention.

FIGURE 1 illustrates a rectangular-screen color television picture tube which may be of conventional construction except for the mounting arrangement of the aperture mask. The tube comprises an envelope composed of a glass faceplate section 21, a glass funnel section 22, and a glass neck section 23 which are frit-sealed together after assembling the internal components of the tube. In the neck section 23 are provided three electron guns 24, 25 and 26 and a conventional accelerating and focusing electrode system 27, and the tube further comprises a final anode 28 in the form of an internal conductive wall coating, to which is connected a contact terminal or anode button 29. On the inner substantially spherically curved surface of the generally rectangular end portion or screen portion 30 of faceplate section 21 is provided an aluminized mosaic phosphor screen 31 which, in an illustrative embodiment, may constitute a conventional tri-color phosphor dot screen composed of three interspersed groups of phosphors emitting visible radiation of different primary colors, e.g., red, blue and green, in response to electron bombardment. The tube further comprises a color-selection device 32 composed of a rigid metal frame 33 to which is aflixed a generally rectangular aperture mask 34 having a curvature generally corresponding to that of mosaic screen 31 and having an aperture pattern corresponding to the distribution pattern of the individual component phosphors of mosaic screen 31. Color-selection device 32 must be precisely spaced from and aligned with the mosaic phosphor screen 31 in order to insure that the electron beams originating at guns 24, 25 and 26 may each have access only to individual phosphor components of screen 311. The entire construction may be conventional with the exception of the mounting arrangement for color-selection device 32.

In accordance with the invention claimed in the aboveidentified copending application, color-selecti-ondevice 32 is mounted to faceplate section 21 of the envelope in the required precise predetermined space relation with mosaic phosphor screen 31 by means of three cantilever springs 35, 36 and 37 which, as best seen in FIGURE 2, are aflixed to generally rectangular frame 33 of color-selection device 32. Springs 35, 36 and 37 are respectively provided with outwardly directed tapered studs 38, 39 and 40 respectively, each of which is of a length less than the substantially uniform distance between frame 33 and the internal surface of rim portion 41 of faceplate section 21. They are of tapered configuration, preferably extruded of stainless steel having a cross-section of Y-configuration, as best seen in FIGURE 7, although other forms of substantially triangular cross-section are also appropriate. Spring 36 is afiixed .to frame 33 with its stud 39 at the center of one of the longer legs of the rectangular frame, while springs and 37 are afiixed to frame 33 with their studs 38 and at opposed locations on the shorter legs substantially threefourths of the distance from the leg to which spring 36 is affixed. Studs 38, 39 and 40 are outwardly biased by cantilever springs 35, 36 and 37 respectively, all of which are outwardly biased in a common circumferential direction, e.g., counterclockwise around the frame as viewed in FIGURE 2. Studs 38, 39 and 40 are received in respective metal sockets such as socket 42 in FIGURE 1 which are sealed in recesses provided in internally projecting bosses 43, 44 and 45 (FIGURE 2) which are integral with rim portion 41 of faceplate 21. The engagement between the male and fem-ale support members is shown in detail in FIGURES 5-7.

This mounting construction provides a positive-locking firm support for color-selection device 32, securing the latter in a fixed position which is duplicated precisely each time the color-selection device 32 is removed and reinserted during the processing of the phosphor screen. Moreover, the bias of springs 35, 36 and 37 is made sulficiently strong to maintain all of the studs 38, 39 and 40 in mating engagement with their respective sockets even upon temporary lateral displacement of frame 33 by a maximum distance in any direction, as may be encountered upon severe shock. The frame is prevented from substantial movement in either the upward or downward direction as viewed in FIGURE 2 by virtue of the positive engagement of studs 35 and 37 in their respective sockets, and if the frame is displaced laterally in either .ing arrangement also achieves a greatly improved degree of precision, relativeto prior art constructions, in thealignment of color-selection device 32 with respect to the phosphor screen 31, and this objective is achieved with greater uniformity and at lower cost in mass production than can be obtained with presently employed methods.

In order to facilitate a more complete understanding of the merits and advantages of the constructions and methods of the present invention, a detailed understanding of the mounting arrangements and processing techniques employed in the manufacture of conventional color television picture tubes will be helpful. FIGURES 3 and 4 illustrate the essential features of the presently employed mounting construction; for convenience, the corresponding components of the mask and screen assembly are designated by corresponding primed reference numerals. As seen in FIGURE 3, rim portion 41' of faceplate section 21' is provided with a plurality of support pins 50, of which only one is shown, Which are fused into the glass of the rim portion. correspondingly situated female support members in the form of cantilever springs 51, only one of which is shown in FIGURE 3, which are secured to frame 33' and are provided with triangular apertures 52, adapted for mating engagement with pins 5t as shown more specifically in FIGURE 4.

In manufacturing a device of conventional construction, as shown in FIGURES 3 and 4, the glass faceplate 21 with integral screen and rim portions 39' and ii is molded of an appropriate glass such as type 9019 furnished by Corning Glass Company. This glass has a softening point around 683 C. and a strain point of approximately 450 C. After molding, the faceplate section 21 is annealed by raising it to a temperature above the annealing point 490-500 C., and then gradually reducing the temperature at a rate of about 2 a minute to an end temperature well below the strain point, e.g., 350 C., after which it may be rapidly cooled to room temperature. During the annealing operation, the faceplate section is maintained in an inverted position, with the screen portion up, resting on the exposed edge of rim portion 41. The annealing operation is required in order to relieve internal stresses inherent in the molding operation, and although the glass is not'appreciably softened at the annealing temperatures, the Weight of the screen portion 39' is sufficiently great that a small but measurable and significant amount of sagging is usually encountered. The tolerances in color television picture tubes, and particularly in the mask and screen assembly, are sufiiciently critical that only .a very small amount of sagging can be tolerated; for mass production purposes, a maximum deviation from the prescribed spherical curvature of plus or minus .020 inch has been found to represent a practical limit; with care, this tolerance range can be maintained during the annealing operation.

The faceplate section 21 is then withdrawn from the annealing oven and pins 56) are inserted by locally softening the glass above its melting point, inserting the metal pins 50 with an appropriate jig or fixture, and cooling whereupon the pins are fused to the glass rim. This process, however, creates internal stresses and strains in the faceplate section 21' and consequently it isnecessary to re-anneal the faceplate section after insertion of pins 59. The re-annealing operation is attended by a further sagging or warping of the screen portion, which adds to that resulting from the original annealing operation. It is extremely difiiicult to maintain the total sag within the nominal .020 inch tolerance range; consequently, a large number, which may be as high as 80% or 85%, of

Pins Sit are engaged by mass produced faceplates are rejected for falling outside the required tolerance range. Moreover, the re-annealing operation may also result in a slight canting or misalignment of one or more of the support pins 50, with a re sultant instability or misalignment of the mask assembly.

In the manufacture of a color television picture tube in accordance with the present invention, a much greater degree-of precision is maintained in that the positioning of the color-selection device is rendered substantially independent of the more difficultly maintained tolerances in dimensions of glass parts. In the preferred manufacturing method of the invention, employing the construction shown in FIGURES l, 2 and 5-7, this is achieved by affixing metal sockets or female support members 42 to rim portion 41 as a part of the original molding operation.

FIGURE 8 and FIGURE 9 illustrate an exemplary form 'of apparatus for accomplishing this objective. The apparatus includes a three-part mold including a conventional. dish section 69, a plunger section 61, and. a retain-ing ring 62 which, as shown in FIGURE 8, is centrally split into two parts 62a and 62b. Dish section and plunger section 61 are contoured to provide the requisite faceplate curvature. A charge of molten glass is placed in dish section 68, plunger 61 is inserted and retaining ring 62 clamped in place to mold or cast the faceplate section Zil including integral bosses 44. Plunger section 6-1 is provided with cooling fins 63, and is watercooled by means of a circulating system including inlet and outlet ducts 6 and 65 respectively.

Plunger sect-ion 61 is equipped with three pistons 66, 67 and 63 which are operated by compressed air through ducts 6% and 79. To each of the pistons 66, 67and 68 is connected an outwardly extending plunger rod such as rod 71 in FEGURE 9. Plunger rod 71 is slidable in a tube '72 inserted in the plunger section 61 of the glass mold, and tube '72 is vented with longitudinal slots 73 communicating with a well M at the top of plunger section 71. Communicating with plunger rod receiving tube '72 is a magazine '75 for receiving a plurality of metal eyelets or socket members 42 to be inserted in the rim portion of faceplate section 21. Means are provided for heating the eyelet, such means being schematic-ally shown in the form of gas jets 76communicating with well 74.

When the charge of molten glass is placed in the mold, pistons 66, 67 and 68 are driven outwardly to a position in which the end of plunger rod 71 is flush with the outer surface of the plunger mold section 61, closing off the end of tube 72. When the glass has taken a partial set, but while it is still in a softened or semi-molten condition, the plunger rods are driven outwardly to a maximum displacement determined by adjusting nuts 77. This preforms a recess or well in the boss 44 for receiving the' eyelet which is inserted by first returning the plunger to the position indicated in FIGURES 8 and 9. The eyelet is then fed into tube '72 from magazine 75. Plungers 66, 67 and 63 are again driven laterally, forcing eyelets 42 into the semi-molten bosses 44 of rim portion 41. The plane of engagementtplane 77 of FIGURE 6) of the metal eyelet or socket member 42 with its associated stud, as so inserted into the glass boss 44, is thus precisely indexed relative to the axis of the tube envelope, adjusting nuts '77 being set to provide the desired spacing from the axis. The glass is then permitted to cool, after which the usual annealing operation is performed by placing the faceplate section 21 in an inverted position, with the screen portion 3% up, in an annealing oven, raising the temperature to about 500 C., and slowly reducing- V the temperature at a rate of about 2 C. per minute to a terminal temperature of 350 C. At this point, the annealing operation is complete and subsequent handling of the faceplate does not significantly affect any of the critical dimensional relationships.

In this manner, the metal support members 42 are affixed to the rim portion 41 of faceplate section 21 as a part of the molding operation in which the faceplate itself is formed, and the critical dimensional relationships with reference to the tube axis are independent of the dimensional tolerances of the glass. The processing of the tube is then completed by assembling the colorselection mask to the faceplate section and forming the mosaic phosphor screen on the end portion 30 of faceplate section 21 in any desired conventional manner. In the usual case, the formation of the phosphor screen involves multiple photographic exposures of photo-sensitive resist material through the assembled aperture mask, requiring removal and reinsertion of the mask 32 as many times as there are component phosphors in the mosaic screen. After the phosphor screen is formed, the assembly is completed by bringing the mating pairs of support members 39 and 42 together to securely mount the color-selection device 32 to faceplate section 21 in the desired precise predetermined space relation to the phosphor screen.

In accordance with the invention, the temperature of the faceplate section 21 is maintained below its strain point, e.g., about 450 C. for Corning type 9019 glass, at all times except during the molding and annealing operations. Thus, there is no re-annealing of the faceplate section as in the prior art assembly techniques. The aperture mask 34 may be custom-formed to correspond closely to the contour of the substantially spherical inner surface of end portion 30 on which the phosphor screen is to be deposited, and since there is no subsequent re-annealing operation, this contour remains fixed and is not subject to sagging. Moreover, the position and orientation of the socket members 42 in the rim are determined only by the parameters of the fixture of FIGURES 8 and 9, these elements being unaffected in their location and orientation by the subsequent tube processing. The manufacturing method of the invention not only eliminates an expensive and time-consuming reannealing operation, but also enables the critical manufacturing tolerances to be maintained in mass production. Since the prior art fabricating techniques have led to reject rates as high as 80% or 85% of the studded faceplates, a major cost saving is accomplished by the constructions and techniques of the present invention.

In accordance with another embodiment of the invention, the female support members or sockets may be installed after the molding and annealing of the faceplate section. Such a construction is illustrated in FIGURES l and 11, which show the engagement between stud 39 and a socket 80 which is sealed within a recess 81 in a preformed boss 82 on the internal surface of rim portion 41 of the faceplate section by means of a glass frit 83. Boss 82 is also formed, as a part of the molding operation, with an indexing surface in the form of a V-shaped notch 84 adjacent the recess 81 which receives the metal support member 80, as shown in FIGURE 11. Indexing notches 84 determine a reference plane, substantially parallel to a plane tangent to the spherically curved screen portion of faceplate 21, from which the mask forming and socket locating operations are indexed. It will be understood that three such bosses are provided in appropriate locations to receive the studs which are spring mounted to the frame 33 of the color-selection mask, and that each is provided with an adjacent indexing notch 84.

To secure the requisite degree of accuracy, comparable to that obtained with the previously described embodiment in which the metal socket members 42 are affixed to the faceplate section as a part of the molding operation, blank metal pads are frit-sealed in the recesses before the formation of the stud receiving sockets 85. If the faceplate is of Corning type 9019 glass, the blank pads may be composed of industry type 446 stainless steel having a thermal coefiicient of ll4 10* inches per degree C. The composition of the glass frit employed is selected to substantially match the temperature coefiicient of expansion of the glass employed in molding the faceplate section. For example, if the faceplate section 21 is formed of Corning type 9019 glass, which has a thermal coefiicient of expansion of approximately l04 10-6 inches per degree centigrade, a commercially available frit having at thermal coefiicient of about 105x10- inches per degree centigrade may be employed; such a frit is available from the Kimble Glass Company under the commercial type designation CV130. The metal pad is coated with the frit, which comes in the form of a paste, and the coated pad is then inserted in the recess 81 and fired at a temperature below the strain point of the glass; the CV13O Kimble frit fires at a temperature of 440 C. The amount of frit applied is not critical, since the pad is inserted before the socket 85 is formed.

The indexing notches 84, which are preformed in the bosses as a part of the molding operation, are all oriented or directed toward the axis of the tube envelope. The faceplate section 21, with the blank metal pads atfixed, is then placed screen portion down and a jig or fixture inserted as shown in FIGURE 12. The fixture is provide with indexing elements 90, 91 and 92 of generally spherical configuration which are radially directed with respect to an axis corresponding to that of the tube envelope and which engage the indexing notches 84 in the bosses. The engagement of indexing elements 91 and 92 with the associated notches in the faceplate bosses is shown in FIGURES 14a and 14b, respectively, in which the blank metal pads 93 and 94 are also illustrated. The engagement of spherical indexing elements 90, 91 and 92 with the indexing notches provides a uniquely determined stable support for the processing fixture shown is FIG- URES 12 and 13.

The fixture comprises a frame 95 on which are mounted three electric drills, of which one is shown at 96 in FIGURE l3. Associated with the drills, which are mounted for lateral movement on frame 95, are associated compressed-air-operated pistons, such as 97 in FIGURE 13, which are spring-biased inwardly of the faceplate. Upon the application of compressed air to the operating pistons, the drill 96 moves laterally to the right until a stop member 98 engages an adjusting screw 99 which determines the maximum lateral traverse of the drill 96. The drill is provided with a bit 100 which engages the blank metal pad 94 and forms the stud receiving socket 85 shown in FIGURES 10 and 11; the engagement plane of socket 85 with its associated mounting stud on the frame is thus determined solely by the fixture of FIGURES 12 and 13 and may be preset by adjusting screw 99.

After formation of the stud receiving sockets in the blank metal pads, the processing of the tube is completed in the same manner as in the previously described embodiment, being certain to maintain the temperature of the faceplate section below its strain point at all times except during the molding and annealing operations.

Accordingly, the same advantages specified with respect to the previously described process are achieved.

In the previously described embodiments, the male support members or studs are affixed to the cantilever springs on the aperture mask frame, and the female support members or sockets are afiixed to the rim of the faceplate section. It is also possible to obtain the beneficial results and advantages of the present invention in a construction in which the support members on frame and faceplate are reversed. Thus, as shown in FIGURE 15, the female support members may constitute cantilever springs such as mounted to the frame of the color-selection mask, and each provided with a triangular aperture for receiving a tapered conical stud 111 which is pressed or otherwise secured in a pre-drilled metal pad 112 frit-sealed into a preformed recess in the internal boss of the faceplate section rim. In order to secure the benefits of the invention, the taper should be put on the stud 111 after insertion of the latter in the metal glass.

pad 112; this can be achieved with a fixture similar to that shown in FIGURES l2 and 13, in Which the drill bits 100 are replaced with cutting tools similar to those employed in a conventional pencil sharpener.

Thus the invention provides a new and improved manufacturing technique for the production of color television picture tubes, with which the degree of precision alignment between the color-selection device and the mosaic phosphor screen is greatly enhanced, and with which such tubes can be produced in large quantities without encountering excessive manufacturing rejects attributable to alteration of the configuration of the glass faceplate after insertion of the support members. These advantages are achieved by maintaining the glass faceplate at a temperature below its strain point at all times except during the initial molding and annealing operations.

The metal support members may be affixed to the faceplate either as part'of the original molding operation or subsequent to the molding and annealing operations by frit-sealing at temperatures below the strain point of the In all cases, the plane of engagement of each stud with its mating socket is determined exclusively by reference to the axis of the tube envelope and is therefore independent of the variations in dimensions within the working tolerance range of the glass.

The invention provides not only a substantially reduced manufacturing cost, but also results in a construction in which the rendition of both color images and monochrome images is enhanced by virtue of the higher degree of precision in manufacturing tolerances; The cost reduction achieved may be of the order of several dollars per tube, and the techniques of the invention permit the use of faceplate sections fabricated for monochrome picture tubes to be employed, with but minor modification, in the manufacture of color tubes.

In processing the tube, particularly in laying down the tri-color screen, it is frequently necessary to remove residual screening material from faceplate section 21. It is customary to use a blade which is driven around the inner periphery of the rim 41 in removing such material. The prior tube structure, featuring studs projecting radially inward from the rim as shown in FIGURE 3, impedes the wiping operation but this difficulty is'avoided in the described structures wherein the bosses, such as 43, 44 and 45, are circumferentially tapered on both sides to merge gradually to the inner wall of rim portion 41. Because of theneed to accommodate this wiping action, it is preferred that the female of the pairs of supporting devices be accommodated within such bosses.

The described bosses are preferably cast into the tube faceplate section whether the eyelets 42 are utilized as in the structure of FIGURE6 or whether the blanks 80 of FIGURE 11 are employed. In either case there is a possibility of scratching at the time the metal insert or the mask assembly is placed in position. However, any such scratching occurs on the surfaces of the bosses rather than on the faceplate panel itself. In this way, weakening of the faceplate through scratching is avoided. Further protection from scratching may be realized by ribbing the bosses, that is, by casting a series of ribs on the inner face of the bosses spaced from one another and extending perpendicular to the direction in which mask 34 is inserted.

It should be noted that the V-shaped notches 84 provide positive gage points as references against which measurements may be accurately made to check the desired conformation of the faceplate. Additionally, they locate the mask-holding fixtures independently of variations in contour of the faceplate and thus avoid another diliiculty of the prior tube structures.

While particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing f-rom the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

I claim:

1. In the manufacture of a color television picture tube of the type comprising an envelope having substantial symmetry with respect to a predetermined axis and composed of a glass faceplate section with an end portion and a rim portion, and a funnel section sealed to said faceplate section, a mosaic phosphor screen on the inner surface of said end portion of said faceplate section, and a multi-apertured color-selection device having a rigid frame and a mask element with an aperture pattern corresponding to the distribution pattern of the component phosphors in said mosaic screen, the method of mounting said color-selection device in a precise predetermined space relation to said phosphor screen by the use of mating pairs of male and female support members adapted for spring-biased mutual engagement in predetermined respective engagement planes, which method comprises:

molding and annealing said glass faceplate section; securing to said frame, at circumferentially spaced locations thereon and in outwardly directed orientation with respect thereto, a first support member of each mating pair, whereby said first support members are maintained in predetermined mutually spaced relation to each other; affixing the other support member of each of said mating pairs to said rim portion of said faceplate section with its plane of engagement with the associated first support member at an accurate predetermined distance from said axis, and with said other support members positioned in a circumferential array accurately corresponding to said predetermined mutually spaced relation of said first support members;

' maintaining the temperature of said faceplate section below its strain point at all times except during said molding and annealing operations;

forming said phosphor screen on said end portion of said faceplate section;

and bringing said mating pairs of support members together to securely mount said color selection device to said faceplate section in said precise predetermined space relation to said phosphor screen.

2. The method of claim 1, in which said other support members are affixed to said faceplate section as a part of said molding operation.

3. The method of claim 1, in which said first support members are male support members and said other sup-' port members are affixed to said faceplate section after completion of said molding and annealing operations by frit-sealing metal members to said rim portion in approximately the desired locations, and thereafter precision drilling said metal members to form receptacles for said first support members with their engagement planes at said accurately predetermined distance from said axis.

4. The method of claim 1, in which said first support members are said female support members and said other support members are affixed to said faceplate section after completion of said molding and annealing operation by frit-sealing recessed metal members to said rim portion in approximately the desired location, inserting pins in the recesses of said metal members, and thereafter precision tapering said pins to locate the engagement planes of said mating pairs of support members at said accurately predetermined distances from said axis.

5. In a manufacture of a color television picture tube of the type comprising an envelope having substantial symmetry with respect to a predetermined axis and composed of a glass faceplate section with an end portion and a rim portion, and a funnel section sealed to said faceplate section, a mosaic phosphor screen on the inner surface of said end portion of said faceplate section, and a multi-apertured color-selection device havinga rigid frame and a mask element with an aperture pattern corresponding to the distribution pattern of the component phosphors in said mosaic screen, said color-selection device being maintained in a precise predetermined space relation to said phosphor screen, the method comprising:

molding and annealing said glass faceplate section to include in addition to said end portion and said rim portion, a plurality of circumferentially spaced indexing surfaces, oriented toward said axis and spaced from a plane tangent to said end portion by a substantially uniform distance, defining a reference plane substantially parallel to said tangent plane;

securing to said frame at correspondingly circumferentially spaced peripheral locations thereon a plurality of cantilever springs outwardly biased in a common circumferential direction, said springs bearing outwardly directed tapered studs of generally triangular configurations;

forming said multi-apertured mask element to a contour with respect to said reference plane substantially corresponding to that of the internal surface of said end portion of said face-plate section; securing said mask element to said frame; providing a corresponding plurality of metal sockets affixed to the interior wall of said rim portion at locations equi-distant from said indexing surfaces;

inserting said studs in said sockets to mount said colorselection device in precisely spaced juxtaposition with said end portion of said faceplate section;

maintaining the temperature of said faceplate section below its strain point at all times except during said molding and annealing operations;

forming said phosphor screen on said end portion of said faceplate section by the use of as many photographic processes as there are component phosphors in said mosaic screen, each such process including exposure through said mask element and subsequent removal of said color-selection device;

and reinserting said studs in said sockets to mount said color-selction device in said precise predetermined space relation to said phosphor screen.

6. In the manufacture of a color television picture tube of the type comprising an envelope having substantial symmetry with respect to a predetermined axis and composed of a glass faceplate section with an end portion and a rim portion, and a funnel section sealed to said faceplate section, a mosaic phosphor screen on the inner surface of said end portion of said faceplate section, and a multi- 12 apertured color-selection device having a rigid frame and an aperture pattern corresponding to the distribution pattern of the component phosphors in said mosaic screen, the method of removably and reinsertably mounted said color-selection device in a precise predetermined space relation to said phosphor screen by the use of mating pairs of male and female support members adapted for spring-biased mutual engagement in a predetermined engagement plane, which method comprises:

molding and annealing said glass faceplate section; securing to said frame, at circumferentially spaced locations thereon and in outwardly directed orientation with respect thereto, a first support member of each mating pair, whereby said first support members are maintained in predetermined mutually spaced relation to each other; providing a fixture having a corresponding plurality of outwardly movable operating elements having respective intermediate operating positions in which their mutually spaced relation corresponds to that of said selected support members on said color-selection device; longitudinally and circumferentially indexing said fixture relative to said faceplate section to an orientation corresponding to the desired orientation of said selected support members in the completed assembly of said tube; utilizing said operating element of fixture to affix the other support member of each of said mating pairs to said rim portion of said faceplate section with its support plane at a precise predetermined distance from said axis; forming said phosphor screen on said end portion of said faceplate section; and bringing said mating pairs of support members together to securely but removably mount said colorselection device to said faceplate section in asid precise predetermined space relation to said phosphor screen.

References Cited by the Examiner UNITED STATES PATENTS RICHARD H. EANES, JR., Primary Examiner 

1. IN THE MANUFACTURE OF A COLOR TELEVISION PICTURE TUBE OF THE TYPE COMPRISING AN ENVELOPE HAVING SUBSTANTIAL SYMMETRY WITH RESPECT TO A PREDETERMINED AXIS AND COMPOSED OF A GLASS FACEPLATE SECTION WITH AN END PORTION AND A RIM PORTION, AND A FUNNEL SECTION SEALED TO SAID FACEPLATE SECTION, A MOSAIC PHOSPHOR SCREEN ON THE INNER SURFACE OF SAID END PORTION OF SAID FACEPLATE SECTION, AND A MULTI-APERTURED COLOR-SELECTION DEVICE HAVING A RIGID FRAME AND A MASK ELEMENT WITH AN APERTURE PATTERN CORRESPONDING TO THE DISTRIBUTION PATTERN OF THE COMPONENT PHOSPHORS N SAID MOSAIC SCREEN, THE METHOD OF MOUNTING SAID COLOR-SELECTION DEVICE IN A PRECISE PREDETERMINED SPACE RELATION TO SAID PHOSPHOR SCREEN BY THE USE OF MATING PAIRS OF MALE AND FEMALE SUPPORT MEMBERS ADAPTED FOR SPRING-BIASED MUTUAL ENGAGEMENT IN PREDETERMINED RESPECTIVE ENGAGEMENT PLANES, WHICH METHOD COMPRISES: MOLDING AND ANNEALING SAID GLASS FACEPLATE SECTION; SECURING TO SAID FRAME, AT CIRCUMFERENTIALLY SPACED LOCATIONS THEREON AND IN OUTWARDLY DIRECTED ORIENTATION WITH RESPECT THERETO, A FIRST SUPPORT MEMBER OF EACH MATING PAIR, WHEREBY SAID FIRST SUPPORT MEMBERS ARE MAINTAINED IN PREDETERMINED MUTUALLY SPACED RELATION TO EACH OTHER; AFFIXING THE OTHER SUPPORT MEMBER OF EACH OF SAID MATING PAIRS TO SAID RIM PORTION OF SAID FACEPLATE SECTION WITH ITS PLANE OF ENGAGEMENT WITH THE ASSOCIATED FIRST SUPPORT MEMBER AT AN ACCURATE PREDETERMINED DISTANCE FROM SAID AXIS, AND WITH SAID OTHER SUPPORT MEMBERS POSITIONED IN A CIRCUMFERENTIAL ARRAY ACCURATELY CORRESPONDING TO SAID PREDETERMINED MUTUALLY SPACED RELATION OF SAID FIRST SUPPORT MEMBERS; MAINTAINING THE TEMPERATURE OF SAID FACEPLATE SECTION BELOW ITS STRAIN POINT AT ALL TIMES EXCEPT DURING SAID MOLDING AND ANNEALING OPERATIONS; FORMING SAID PHOSPHOR SCREEN ON SAID END PORTION OF SAID FACEPLATE SECTION; AND BRINGING SAID MATING PAIRS OF SUPPORT MEMBERS TOGETHER TO SECURELY MOUNT SAID COLOR SELECTION DEVICE TO SAID FACEPLATE SECTION IN SAID PRECISE PREDETERMINED SPACE RELATION TO SAID PHOSPHOR SCREEN. 